1. Field of the Invention
The present invention relates, generally, to zoom lenses, and in particular embodiments, to an optionally rotatable compound zoom lens that provides a wide focal length range and a wide field of view and is small in size to fit in consumer products such as cellular telephones and other products with compact cameras.
2. Description of Related Art
Notably lacking in the prior art are zoom lenses having a zoom ratio greater than four combined with a maximum field of view at the short focal length position of 85 degrees or more. Although such zoom lenses are known in the field of broadcast zoom lenses, these are typically large, complex and expensive designs. Examples can be found in U.S. Pat. No. 5,745,300, and in Japanese Patents 62-153,913; 08-136,808; 09-015,501; 09-033,812; and 11-030,749.
A more compact, wide-range, wide-angle zoom can be found in U.S. Pat. No. 6,038,084, although the performance of the examples is poor despite significant complexity.
Recently a novel compound zoom system was described in U.S. patent application Publication No. 20040021953, the contents of which are incorporated herein by reference. This system comprises a zoom lens that forms an intermediate image, followed by a zooming relay that re-images the intermediate image to a final image plane. Such a design approach has a number of potential advantages over conventional zoom lens designs, including large zoom range, wide field of view, high image quality, and flexibility in arranging fold mirrors or prisms. However, the zoom system disclosed in U.S. patent application Publication No. 20040021953 does not provide for a compact wide-range wide-angle zoom lens that is suitable for mass-market applications.
Therefore, there is a need for a compact and relatively simple zoom lens with both a wide zoom range and wide field angle that can be economically produced in high volume. Such a zoom lens would have wide-ranging applications in digital still and video cameras, cell phones, PDA's, and the like.